A binaural excursion of ambience through Sydney churches

St Mary’s Cathedral

Location: St Mary’s Cathedral
Time: 6.30pm, Wednesday 31st May, 2017

A stunning piece of Gothic Revival architecture, the cathedral (originally designed by William Wardell in 1865) is the spiritual home of Sydney’s Catholic community and it is the seat of the Archbishop of Sydney. The walls and interior columns are made of yellowed sandstone, a feature that gives an impression of vast strength, whilst the roof is designed using double hammer beam construction with the ceiling being vaulted in dark grain timber. Underfoot, mosaic tiled floors reflect the light that shines in from the stained glass windows that run along the length of the nave.

Figure 1. From the front of the cathedral looking toward the rear doors.

Despite the cavernous volume, the interior auditory atmosphere was very quiet. Large glass and wooden doors seal off the outside world however it was still somewhat surprising to think that just metres away was all the hustle and bustle of a thriving metropolis. Muffled exterior environmental and traffic sounds could only just be heard whilst recording, a 5 minute background noise recording demonstrates the continuous level across octave bands 63Hz to 16kHz.

Figure 2. A build up of low frequency energy which is expected in a space of this size. A lack of interior excitation signals resulted in very low high frequency energy.

Three impulse responses using a balloon pop as the excitation signal were recorded at separate locations within the church. Figure 3 shows the averaged reverberation time was between 1.5 seconds to 5.5 seconds. Figure 4 demonstrates the frequency spectrum as a function of level.

Figure 3. Impulse response measurements across three locations and reverberation times. Construction materials and volume has resulted in a very long reverb time especially through the mid to low frequency range.

Figure 4. Frequency response shows a sharp roll-off in the high frequencies, however this is most likely due to the nature of the balloon pop energy spectrum.

A series of three binaural recordings were conducted from the rear, middle and front of the church. In general, there were very few interior excitation signals with most interest in the recordings being due to the way the exterior sounds rose and fell dynamically and the impact this had upon the cathedral atmosphere. It was quite an unusual sensation to be in such a large voluminous space that was very subdued but at the same time feeling as though it was part of a greater environmental auditory scene.